Biliary Elimination

Question 1

Define EHC

Answer 1

Enterohepatic cycling

Question 2

How could you recognise a drug that undergoes EHC?

Answer 2

Multiple peaks on concentration-time profile

Question 3

True or false = all PK formulas account for EHC

Answer 3

False. Cannot use many of these formulas for EHC drugs. E.g. cannot use CL = dose / AUC

Question 4

Does EHC effect PK or PD?

Answer 4

Both.
PK= increases exposure to drug
PD = prolongs drug’s effects

Question 5

What stimulates bile secretion?

Answer 5

Fat in lumen of duodenum - fatty meal is best
- stimulates CCK release, causing contraction of gall bladder

Question 6

What characteristics increases the likelihood a drug undergoes EHC?

Answer 6

• MW over 500 Da
• polar

Question 7

Briefly describe EHC / biliary elimination

Answer 7

Some of dose will get absorbed from gut lumen, some will go through portal circulation into the liver. Of the portion that enters the liver, some gets sent to the gall bladder, where it is stored. Then will get released from the gall bladder back into the gut lumen, where it can be absorbed into circulation (resulting in second peak on curve + increase in AUC / exposure)